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Improved species concentration measurements using a species-specific weighting procedure on rotational CARS spectra

Vestin, Fredrik LU ; Afzelius, Mikael LU and Bengtsson, Per-Erik LU (2005) In Journal of Raman Spectroscopy 36(2). p.95-101
Abstract
Rotational coherent anti-Stokes Raman spectroscopy (CARS) is used for measurements of temperatures and relative species concentrations. The evaluation of a rotational CARS spectrum is normally performed using a least-squares fitting algorithm to find the best-fit theoretical spectrum in a library of spectra calculated at different temperatures and relative concentrations. A general problem is that species with weak spectral features have a minor influence on the results in the standard evaluation procedure. A species-specific weighting (SSW) procedure enhancing the influence of weak spectral features in the spectral fitting algorithm has therefore been developed. The SSW procedure was tested on the evaluation of low concentrations Of 02 in... (More)
Rotational coherent anti-Stokes Raman spectroscopy (CARS) is used for measurements of temperatures and relative species concentrations. The evaluation of a rotational CARS spectrum is normally performed using a least-squares fitting algorithm to find the best-fit theoretical spectrum in a library of spectra calculated at different temperatures and relative concentrations. A general problem is that species with weak spectral features have a minor influence on the results in the standard evaluation procedure. A species-specific weighting (SSW) procedure enhancing the influence of weak spectral features in the spectral fitting algorithm has therefore been developed. The SSW procedure was tested on the evaluation of low concentrations Of 02 in mixtures with N-2, and it is shown that both the accuracy and precision of single-shot spectra concentration measurements are improved by use of the SSW evaluation procedure. Also, a comparison with previously used weighting procedures shows that this approach is superior. The application of the technique to oxygen concentration measurements in the product gas of a fuel-lean flame is demonstrated. In addition, a test was made using the developed weighting procedure for thermometry, by applying spectral weighting to the rotational spectrum originating from the first thermally excited vibrational state. The precision of the temperature measurements was then slightly improved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
concentration measurements, rotational CARS, combustion diagnostics
in
Journal of Raman Spectroscopy
volume
36
issue
2
pages
95 - 101
publisher
John Wiley & Sons
external identifiers
  • wos:000227253400003
  • scopus:14544277039
ISSN
1097-4555
DOI
10.1002/jrs.1294
language
English
LU publication?
yes
id
4369ab2c-3025-4363-86ce-4d92ce53264c (old id 251741)
date added to LUP
2007-08-15 16:14:24
date last changed
2017-01-01 06:53:17
@article{4369ab2c-3025-4363-86ce-4d92ce53264c,
  abstract     = {Rotational coherent anti-Stokes Raman spectroscopy (CARS) is used for measurements of temperatures and relative species concentrations. The evaluation of a rotational CARS spectrum is normally performed using a least-squares fitting algorithm to find the best-fit theoretical spectrum in a library of spectra calculated at different temperatures and relative concentrations. A general problem is that species with weak spectral features have a minor influence on the results in the standard evaluation procedure. A species-specific weighting (SSW) procedure enhancing the influence of weak spectral features in the spectral fitting algorithm has therefore been developed. The SSW procedure was tested on the evaluation of low concentrations Of 02 in mixtures with N-2, and it is shown that both the accuracy and precision of single-shot spectra concentration measurements are improved by use of the SSW evaluation procedure. Also, a comparison with previously used weighting procedures shows that this approach is superior. The application of the technique to oxygen concentration measurements in the product gas of a fuel-lean flame is demonstrated. In addition, a test was made using the developed weighting procedure for thermometry, by applying spectral weighting to the rotational spectrum originating from the first thermally excited vibrational state. The precision of the temperature measurements was then slightly improved.},
  author       = {Vestin, Fredrik and Afzelius, Mikael and Bengtsson, Per-Erik},
  issn         = {1097-4555},
  keyword      = {concentration measurements,rotational CARS,combustion diagnostics},
  language     = {eng},
  number       = {2},
  pages        = {95--101},
  publisher    = {John Wiley & Sons},
  series       = {Journal of Raman Spectroscopy},
  title        = {Improved species concentration measurements using a species-specific weighting procedure on rotational CARS spectra},
  url          = {http://dx.doi.org/10.1002/jrs.1294},
  volume       = {36},
  year         = {2005},
}